Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation and Cash-Based Incentive Compensation (Schedule of Incentive Compensation Expense) (Detail)

v2.4.0.6
Share-Based Compensation and Cash-Based Incentive Compensation (Schedule of Incentive Compensation Expense) (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Share-based compensation charged to operating income $ 3,319 $ 2,775 $ 9,137 $ 6,437
Cash-based incentive compensation charged to operating income 3,995 3,721 7,772 12,011
Total incentive compensation charged to operating income 7,314 6,496 16,909 18,448
Parent Company [Member]
        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Share-based compensation charged to operating income 3,319 2,775 9,137 6,437
Lease Operating Expense [Member]
        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Share-based compensation charged to operating income   116   349
Cash-based incentive compensation charged to operating income 947 697 2,846 2,836
General And Administrative [Member]
        
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Share-based compensation charged to operating income 3,319 2,659 9,137 6,088
Cash-based incentive compensation charged to operating income $ 3,048 $ 3,024 $ 4,926 $ 9,175